tick/broadcast: Prevent NULL pointer dereference

Dan reported that the recent changes to the broadcast code introduced
a potential NULL dereference.

Add the proper check.

Fixes: e0454311903d "tick/broadcast: Sanity check the shutdown of the local clock_event"
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index ee3cf942d6ebd18b76c44b71ec8dfecabbc7111b..52b9e199b5acc1e292d7e5a030685f6dbe7fdfe2 100644 (file)
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -409,14 +409,16 @@ void tick_broadcast_control(enum tick_broadcast_mode mode)
                break;
        }
 
-       if (cpumask_empty(tick_broadcast_mask)) {
-               if (!bc_stopped)
-                       clockevents_shutdown(bc);
-       } else if (bc_stopped) {
-               if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
-                       tick_broadcast_start_periodic(bc);
-               else
-                       tick_broadcast_setup_oneshot(bc);
+       if (bc) {
+               if (cpumask_empty(tick_broadcast_mask)) {
+                       if (!bc_stopped)
+                               clockevents_shutdown(bc);
+               } else if (bc_stopped) {
+                       if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
+                               tick_broadcast_start_periodic(bc);
+                       else
+                               tick_broadcast_setup_oneshot(bc);
+               }
        }
        raw_spin_unlock(&tick_broadcast_lock);
 }